This study is on effects of student’s centred method of learning (cooperative learning method) on sexual health knowledge and attitudes of adolescents in Anambra State secondary schools. The inability of adolescents to acquire adequate knowledge regarding sexual health could be due to the method of teaching used which are mainly techer-centred methods such as lecture, discussion, Socratic, demonstration teaching methods among others. Therefore, students’ centered method is recommended in today’s teaching and learning and cooperative learning method is one of them. The main purpose of the study was to determine the mean scores of adolescents in Anambra State secondary schools exposed to cooperative learning method on sexual health knowledge and attitudes and by comparing the scores with that of control group. The study was guided by six research questions and eight hypotheses. Quasi experimental research design was used and the population consisted of 20,342 senior secondary two (SS2) students in Anambra State. One hundred and fourty SS2 students comprised sample for the study using simple random sampling technique without replacement. Four secondary schools in Anambra state were sampled. Then one intact class was sampled from each of the sampled schools using simple random sampling technique without replacement. Two schools were exposed with cooperative learning method and the other two schools were used as control group for six weeks. The instruments for data collection were Sexual Health knowledge Test (SHKT) and Sexual Health Attitudes Questionnaire (SHAQ). Analyses of data were carried out using Mean, Standard Deviation and Analysis of Covariance (ANCOVA). The findings of the study among others revealed that cooperative learning method improved sexual health knowledge and attitudes of the subjects as depicted by the positive gained mean scores recorded more than the control group. Male adolescents exposed to cooperative learning method had better sexual health knowledge gained mean score (X = 37.27) than their female counterparts (X = 32.46) exposed to the same method. But the female adolescents’ standard deviation showed better homogeneity of responses than their male counterparts. Female adolescents exposed to cooperative learning method had better sexual health attitude gained mean score (X = 11.38) and their standard deviation showed better homogeneity of responses than their male counterparts exposed to the same method (X = 9.37). The effect of cooperative learning method on the mean sexual health knowledge and attitudes scores of adolescents in Anambra state secondary schools differ significantly using their post-test mean scores P < 0.05. On the contrary, the effect of cooperative learning method on the mean sexual health knowledge and attitudes scores of male and female adolescents in Anambra state secondary schools did not differ significantly using their post-test mean scores P > 0.05. It was recommended among other things that there is need to include cooperative learning method in handling sexual health education in the school curriculum at all levels of education in Nigeria.